The reason for development was mainly for a ZX81 replica from the german user holmatic which is called ZX81NU with pure discrete logic instead of a ULA.
Many people like a more comfortable keyboard feeling while typing and so the idea was born to build up a keyboard (initiated from german Paul).
So this keyboard can replace any ZX81 membrane while simply putting it on top of the old membrane - so it is fully reversable to keep the original state of a ZX81.
the board itself - smaller in thickness, just 0.8mm instead of the standard 1.6mm, so half in height
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assembled here with the ALPS SKQGAFE010 tactile switches with low profile (1.5mm) and MOLEX jumper cables to easily connect the replacement keyboard to the MOLEX connectors on the ZX81, the jumper cables (type 25001) are flat cables with a half-solid core (drilled and soldered wires on the full length) which give both, flexibility and rigidity
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the jumper cables are passing the hole in the case quite comfortable and the old membrane can be left there or removed - up to you
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Standby alert 